1. Field of the Invention
This invention relates generally to cassette tape recording and reproducing apparatus and, more particularly, to a mechanism for use with such tape recording apparatus to automatically change the direction in which the tape is being driven.
2. Description of the Prior Art
There have been proposed various mechanical and electrical arrangements for use in cassette tape recorders to provide automatic reversing of the tape drive direction. Typically, the direction in which the tape is driven is changed or reversed once the tape is completely unwound from the supply reel to the take-up reel during the playback mode of operation of the tape recorder.
Now, if the tape recorder is capable of recording signals as well as reproducing them, there are at least two different situations that must be considered when providing automatic reversing for such apparatus. One such situation would be that the apparatus would automatically change the tape-drive direction upon detecting the end of the tape, even though the apparatus is in the recording mode. In that case, however, because it is not desirable to record over an already recorded segment, it is therefore necessary to detect whether one or both of the pair of removable tabs, which are formed at the rear corners of all compact audio cassettes have been removed or punched out. These tabs are provided to prevent recording over already recorded material, and it is standard practice to remove the tabs once a recording has been made. Most tape recorders can sense the presence or absence of such tabs by means of switches to lock out the recording system, so that the tape cannot be inadvertently erased and re-recorded. The two tabs on the back wall of the cassette correspond to the two "sides" of the tape. Thus, in any automatic reversing system, a mechanism and electrical circuitry must be provided to detect the presence or absence of both tabs, so that the tape will not be inadvertently erased. Moreover, having such automatic reversing feature places the burden upon the user to pay strict attention to removing the tabs once a program has been recorded. The electrical circuitry and mechanism for detecting the presence of the tabs add to the cost of the unit, as well as to the complexity, and thus affect the reliability of the unit.
Another situation, which is more of a general nature, is the provision of a mechanism and circuitry to automatically stop the tape drive upon the detection of the tape end during the recording mode and to sequentially change the direction of the tape drive upon such tape-end detection during the playback mode. To implement this feature it is necessary to distinguish the recording mode of the apparatus from the playback mode, and this involves additional switches and the like corresponding to the various mode selecting switches of the unit. Also, some means for detecting the tape end must be provided and would typically incorporate logic circuitry connected to all of the switches to generate a control signal for operating a control mechanism, for example, a plunger-solenoid, to initiate the appropriate movements of the tape mechanism, upon detecting the tape end in the selected mode of the tape recorder. Once again, this necessary mechanism and electrical circuitry will increase the number of electrical and mechanical parts and thereby increase the cost of the apparatus. Also, because the typical tape recorder of today is intended for portable use, the miniaturization in size and the requirement to minimize electrical power consumption are of importance.